Influence of normal load and sliding speed on the tribological property of amorphous carbon nitride coatings sliding against Si 3N 4 balls in water

Abstract

Amorphous carbon nitride (a–CN x ) coatings were deposited on Si 3N 4 disks by an ion beam assisted deposition system. The composition, structure and hardness of the a–CN x coatings were characterized by Auger electronic spectroscopy, Raman spectroscopy and nano-indentation tester, respectively. The influences of normal load and sliding speed on the friction coefficients and the specific wear rates for the a–CN x/Si 3N 4 tribo-pairs were investigated and analyzed synthetically by ball-on-disk tribometer. The worn surfaces were observed by optical microscope. The results showed that the a–CN x coatings contained 12 at.% nitrogen, and their structure was a mixture of sp 2and sp 3 bonds. The a–CN x coatings’ nanohardness was 29 GPa. The influence of sliding speed on the friction coefficients and the specific wear rate of the CN x coatings was more obvious than that of normal load. The friction coefficients and the specific wear rate of the CN x coatings decreased as the sliding speed increased. At a sliding speed higher than 0.1 m/s, the friction coefficients were less than 0.04. The specific wear rates of the a–CN x coatings were higher than those of Si 3N 4 balls at a sliding speed below 0.1 m/s, while the specific wear rates of the a–CN x coatings and the Si 3N 4 balls all fluctuated around a lower level of 10 − 8 mm 3/Nm as the sliding speed increased beyond 0.2 m/s. To describe the wear behavior of a–CN x coatings sliding against Si 3N 4 balls in water with normal loads of 3–15 N and sliding speeds of 0.05–0.5 m/s, the wear-mechanism map for the a–CN x /Si 3N 4 tribo-pairs in water was developed.